A method of reproducing sound recorded with microphones arranged around both ears through a headphone is known as a binaural recording/reproduction system. A two-channel signal recorded by the binaural recording is referred to as a binaural signal, which contains acoustic information on a position of a sound source in a lateral direction, and in an up-down direction and a front-back direction as well, to a human. Moreover, a method of reproducing this binaural signal using the two-channel speakers on the left side and the right side, instead of using the headphone, is referred to as a transaural reproduction system (e.g., see Patent Document 1).